U.S. Pat. No. 4,191,001 discloses a method of exteriorly insulating existing concrete block walls by applying furring strips, expanded polystyrene boards over the furring strips, chicken wire stapled to the polystyrene boards, and a concrete coating over the chicken wire and polystyrene boards. The butt joints between boards are sealed with a polystyrene glue. The stapling of the chicken wire and the glueing of the butt joints is relatively time-consuming. Further, the polystyrene board has a relatively high coefficient of thermal expansion. For this reason, the board is frequently applied in relatively small pieces, such as two by four feet, and this requires sealing more joints as well as cutting and putting up more pieces. Also, the concrete coating must have an elastomeric bonding agent to compensate for thermal expansion and contraction of the board. In addition, the polystyrene board encounters resistance by enforcers of fire codes.